1. Field of the Invention
Fitting ophthalmic lenses to spectacles frames with particular reference to means for facilitating determination of minimum lens blank size for given spectacles frame size and/or maximum frame size for given lens blank size.
2. Discussion of the Prior Art
In the preparation of an ophthalmic lens for spectacles glazing, there is the need to select an uncut blank of a size from which the intended spectacles effective diameter (ED) can be obtained with proper lens optical center and/or segment location.
The selection of lens blank size to fit particular spectacles frames and vice versa ordinarily requires complicated calculation, the use of a computer or reliance upon ED charts which require removal of blanks and frames from stock and checking for ED suitability by careful positioning one at a time over the chart. Unsatisfactory blanks and/or spectacles frames are required to be returned to inventory or otherwise set aside. An exemplary ED chart is illustrated in U.S. Pat. No. 3,740,857 wherein the tediousness and drawbacks of method taught are readily apparent.
In view of the above, this invention has the objective of quickly straightforwardly and accurately determining suitable uncut lens blank sizes for edge finishing to particular spectacles frame ED measurements or suitable spectacles ED measurement for particularly selected lens blank sizes, this being accomplished prior to and for facilitating the selection of stock.
Another object is to accomplish the foregoing with minimal cost and complication of equipment, optimum ease of operation and accuracy of findings.
Other objects and advantages of the invention will become apparent from the following description.